substTest is package{
  import person;
  
  substAgeFun(X,V) is X substitute{ age := V }; 
  
  main() do {
    var J := someone{
      name = "Joe";
    }
    
    assert J.age=nonFloat;
    
    K is J substitute { age := 10.0};
    
    assert K.age=10.0;
    assert J.age=nonFloat;
    
    L is substAgeFun(J,10.0);
    assert L = K;
  }
}